1. Field
Exemplary embodiments relate to a silicon solar cell having a selective emitter structure and a method of manufacturing the same.
2. Description of the Background Art
Recently, as existing energy sources such as petroleum and coal are expected to be depleted, interests in alternative energy sources for replacing the existing energy sources are increasing. Among the alternative energy sources, a solar cell has been particularly spotlighted because the solar cell has abundant energy sources and does not cause environmental pollution.
The solar cell is classified into a solar heat cell that generates a vapor required to rotate a turbine using a solar heat, and a solar light cell that converts photons into electric energy using the properties of a semiconductor. Generally, the solar cell means the solar light cell.
The solar cell is divided into a silicon solar cell, a compound semiconductor solar cell, and a tandem solar cell depending on a raw material. The silicon solar cell has been mainly used in a solar cell market.
FIG. 1 is a cross-sectional view schematically showing a structure of a related art silicon solar cell. As shown in FIG. 1, the silicon solar cell includes a substrate 101 formed of a p-type silicon semiconductor and an emitter layer 102 formed of an n-type silicon semiconductor. A p-n junction similar to a diode is formed at an interface of the substrate 101 and the emitter layer 102.
When solar light is incident on the silicon solar cell having the above-described structure, electrons and holes are generated in a silicon semiconductor doped with impurities by a photovoltaic effect. The electrons are generated as a majority carrier in the emitter layer 102 formed of the n-type silicon semiconductor, and the holes are generated as a majority carrier in the substrate 101 formed of the p-type silicon semiconductor. The electrons and the holes generated by the photovoltaic effect are respectively drawn toward the n-type silicon semiconductor and the p-type silicon semiconductor and respectively move to an electrode 103 connected to an upper portion of the emitter layer 102 and an electrode 104 connected to a lower portion of the substrate 101. A current flows by connecting the electrodes 103 and 104 using electric wires.
Recently, in order to reduce a contact resistance between the electrode 103 and the emitter layer 102, a region of the emitter layer 102 connected to the electrode 103 is formed as a heavily doped region, and a region of the emitter layer 102, which is not connected to the electrode 103, is formed as a lightly doped region. Hence, carrier lifetime is improved. Such a structure is called a selective emitter structure.
The selective emitter structure greatly contributes to the efficiency of the silicon solar cell by reducing the contact resistance between the electrode 103 and the emitter layer 102. However, a process for manufacturing the silicon solar cell having the selective emitter structure is complicated and requires much expense.